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NEET levelSingle correct optionDifficulty 1 of 3o4236

The compound shown reacts only very slowly in E2 with strong bases. Which statement explains this?

  1. ABromine is axial and is too crowded for the base to approach
  2. BThe tert-butyl group fixes the ring so that bromine is equatorial, and no beta C-H bond is anti-periplanar to the C-Br bond
  3. CThe tert-butyl group donates electrons and weakens the C-H bonds
  4. DThe ring is too strained to form a double bond

Answer: B

The trans isomer of 1-bromo-4-tert-butylcyclohexane has both groups equatorial in the only populated chair. An equatorial bromine is anti to ring C-C bonds, not to C-H bonds, so E2 needs the unfavourable ring flip that would put the tert-butyl group axial. Hence elimination is very slow.
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